Quantitative Chemistry

Question 1

grams to moles or moles to grams

- How many moles of blank are contained within blank grams of blank?

Answer 1

use molar mass

Question 2

particles to grams

- How many blank atoms are contained in blank grams of blank

Answer 2

• particles= atoms, molecules, FU
• use molar mass
• use avogadros number

Question 3

predicting mass of products

• Nitrogen gas will react with hydrogen gas to produce ammonia. How many moles of hydrogen gas are required to produce .86 moles of NH3?
• N2O5 reacts with water to produce nitric acid. If 1.93 moles of N2O5 react with excess water, how many moles of nitric acid can be produced?

Answer 3

• use molar ratio

Question 4

how to find limiting reactant

Answer 4

• take the given values and do one for each reactant
• convert to g of product
• whichever produces less is the limiting reactant
• that is how many grams of the product are produced

Question 5

theoretical yield

Answer 5

• grams of limiting reactant

- max that can be produced

Question 6

How to find percent yield

Answer 6

• actual yield/theoretical yield X 100

- how much was produced/ max that can be produced (smallest number) X100

Question 7

mass percent of an element

- Find mass percent of iron in FeTiO3

Answer 7

(# of atoms of element)(elements atomic mass) / (formula weight of compound) X 100

molar mass of each element including # of atoms/molar mass of compound X 100

Question 8

Mass percent of a component

- A tablet contains .025 mg of vitamin D, entire tablet has a mass of .115g. calculate mass % of vitamin D

Answer 8

(mass of component in question)/(total mass of substance) X 100

Question 9

Mass percent
- a sample of potassium chlorate (KClO3) is known to contain some impurities. It is found that K makes up 9.50% of the entire mass of the sample. All of the K is comes from the KClO3 compound. Find the mass percent of KClO3 in the sample.

Answer 9

• molar mass of compound/molar mass of element=unknown %compound/given percent element
• Use proportions to solve
• leave percent as is, don’t change to decimal

Question 10

prove mass is conserved in chemical reactions

Answer 10

take calculations and plug them into equation, should be equal on both sides

Question 11

confirm the law of definite proportions

Answer 11

• number you calculated of element/given value of compound X100 should equal molar mass of element/molar mass of compound X 100

Question 12

how to find the empirical formula for the compound

- a compound contained 68.1% carbon, 13.7% hydrogen, and 18.2% oxygen by mass

Answer 12

• assume 100 g sample
• use molar mass to convert grams to moles
• divide all answers by smallest number to get subscripts for the empirical formula

Question 13

How to find molecular formal

Answer 13

• given molar mass of compound/molar mass of empirical formula
• This number is what you multiply the subscripts by

Question 14

a 1.0857 gram sample of a compound containing only carbon, hydrogen, and oxygen was burned in excess oxygen gas. 3.190g of carbon dioxide and 0.9360g of water were produced. Find the empirical formula of the compound.

Answer 14

• convert g each element to corresponding gram of reactant
• convert each of those numbers to moles
• divide by smallest to find empirical formula as usual